CN1081182C - Liquid phase oxidation and carbonylation process synthesizing dimethyl carbonate - Google Patents

Abstract

The invention relates to a process for synthesizing dimethyl carbonate by liquid-phase oxidative carbonylation of methanol, oxygen, carbon monoxide and the like in the presence of a catalyst. A single-tubular reactor and a catalytically-promoted two-component catalyst are used. The catalyst is cuprous chloride, and the co-catalyst is one of several inorganic chloride salts. During the reaction process, the reactant enters from the bottom of the reactor, and the reaction product is discharged from the top of the vapor phase. After separation, the unreacted gas and liquid circulate and enter the reactor respectively for reaction. The reaction can be carried out continuously for more than 200 hours. Reaction conditions: reaction temperature: 80-200°C, reaction pressure: 1.0-4.0MPa. The process method of the invention has the characteristics of simple process equipment, long operation period, high product yield, easy separation and the like.

Description

A kind of process method of synthesizing dimethyl carbonate by liquid-phase oxidative carbonylation

The invention relates to a process for synthesizing dimethyl carbonate (DMC) from methanol (MeOH), oxygen (O ₂ ) and carbon monoxide (CO) in liquid phase carbonylation in the presence of a catalyst.

The process for carbonylation of raw materials MeOH, O ₂ and CO to synthesize dimethyl carbonate is mainly divided into gas-phase method and liquid-phase method. The gas-phase method is represented by the patent of Ube Company in Japan, and the liquid-phase method is represented by the patent of Enichem Company in Italy. represent. For the liquid phase method, there are patent reports, such as the European patent Euro.Patent App1.0460735A2 (1991). In the liquid phase method of Enichem Company in Italy, tank reactors and cuprous chloride catalysts were used, and there were many problems in the production process, such as the leakage of the tank reactor stirring seal, the discharge and separation of catalysts during operation, Equipment corrosion and other issues. Later, Enichem reported an improved process, using a double-tube circulation reactor and a single-component cuprous chloride catalyst. The reaction conditions are as follows: temperature 120° C., pressure 3.0 MPa, catalytic yield 0.5 gDMC/g-Cat.h. However, there are still disadvantages such as complex reactor structure, incompatibility between catalyst and reaction medium, suspension reaction, catalyst recovery, and complicated procedures.

The purpose of the present invention is to adopt a single-tube two-component catalyst system with simpler technology and equipment to implement the process method of methanol liquid-phase oxidative carbonylation to synthesize dimethyl carbonate, that is, to use a single-tube gas-liquid mixed reactor containing The two-component catalytic system of cuprous chloride and co-catalyst can efficiently synthesize dimethyl carbonate.

The catalyst system involved in the present invention is a binary component system. The co-catalyst can be any one of inorganic salts such as magnesium chloride (MgCl ₂ ), calcium chloride (CaCl ₂ ), zinc chloride (ZnCl ₂ ), and potassium chloride (KCl). The molar (mol) ratio of the catalyst to the co-catalyst can be 1:0.5˜1:1.5. The two form a composite catalyst. The water produced in the reaction process dissolves the inorganic salts to form a high-concentration inorganic salt solution in which cuprous chloride is soluble, and because the addition of inorganic salts increases the solubility of cuprous chloride, the catalyst can react with the The medium methanol is mixed into a homogeneous liquid phase, which improves the reaction efficiency. The binary composite catalyst can be used continuously for more than 200 hours and still maintain high activity. At the same time, the reaction system is converted from the suspension system of the single-component catalyst reported in the original related patents to a solution system, which reduces the problems of flow resistance and blockage of the reaction equipment caused by solid suspended particles.

The single-tube reactor is composed of a liquid phase section and a vapor phase section, which account for 2/3 and 1/3 of the total length respectively, and the diameter of the gas phase section is 1.5 to 2 times that of the liquid phase section. The liquid phase section is composed of gas feed inlet, gas distributor, liquid feed inlet, liquid level gauge, defoaming net and other components. During the reaction process, it plays the role of providing a reaction space, and the gas phase section is composed of a gas outlet, a return port, a separation zone, etc., and plays the role of providing a separation of the gas and liquid phases.

The technical process in the present invention is that methanol and composite catalyst are loaded into the liquid phase zone of the single-tube reactor, and the reaction gas (CO+O ₂ ) is fed in, and the reactants (MeOH, O ₂ , CO) all enter from the bottom . The reaction gas used, _O2 can be pure industrial oxygen or oxygen-enriched gas with a purity of 95-99%; CO can be pure carbon monoxide or other industrial waste gas containing CO, and the CO% can be 80-95%, wherein impurities such as N ₂ , H ₂ , O ₂ , CH ₄ , CO ₂ and the like do not have adverse effects on the catalyst. After feeding, the temperature is raised to 80-200°C. After the reaction occurs, the reaction product is partially vaporized and rises to the gas phase area, and the reaction product (DMC, H ₂ O) and raw material gas are discharged from the top of the vapor phase section. In the separation section, due to the action of gravity and the reduction of reaction speed, most of the entrained liquid falls, and the product vapor and unreacted gas-liquid are taken out of the reactor and enter the cooler and vapor-liquid separator. The separated gas enters the circulator and then enters the The reaction is carried out in the liquid phase area at the bottom of the reactor, and the liquid can flow back to the reactor or enter the next separation section. In the separation section, DMC, MeOH, and H ₂ O are rectified to obtain DMC products and discharge H ₂ O , the recovered MeOH is sent to the MeOH storage tank for recycling.

The single-tube reactor involved in the present invention is upright and consists of a liquid phase section and a vapor phase section, accounting for 2/3 and 1/3 of the total length respectively. The pipe diameter of the vapor phase section is 1.5 to 2 times that of the liquid phase section. The pipe diameter of the liquid phase section is 0.1-0.5m, and the length is 2-6m. The reactor can be made of corrosion-resistant alloy materials, or it can be made of corrosion-resistant lining composite metal materials.

The composite catalyst in the present invention can add solid matter from the feed port on the reactor, or can be dissolved with methanol in an external dissolution tank and then pumped into the reactor by methanol. The content of the catalyst in the entire liquid phase system is 2-20%. (W/W).

The single-tube reactor and the binary catalyst system used in the process of the present invention are used for the liquid-phase oxidative carbonylation of methanol to prepare dimethyl carbonate. The reaction temperature is 80-200°C, preferably 100-130°C, and the pressure is 1.0-4.0MPa, preferably 2.0-2.5MPa, CO concentration 80-95%, preferably 85-95%, _O2 concentration 1-15%, preferably 5-7%, _H2O concentration 1-20%, preferably 1-8%, and the space velocity is 200-2000h ^-1 , preferably 400-1000h ^-1 . Under the above conditions, the reaction system can run for a long time, the running time can reach 200-1000h, the methanol conversion rate is 5-20%, the selectivity is 99%, the CO selectivity is 85-95%, and the DMC concentration in the product can be 15% -25%, the content of organic by-products in the product is less than 0.05%. The catalyst yield is 0.5-0.6g DMC/gCat.h.

The composite catalyst in the present invention is deactivated after long-term operation, and can be discharged from the bottom of the reactor, and after methanol is evaporated, a copper-containing residue is obtained. The residue can be conveniently recovered according to conventional inorganic preparation methods to obtain CuCl, and the recovery rate reaches 90-95%.

Compared with the prior art, the reaction system of the present invention is a single-tube reactor and a binary catalytic system, which greatly simplifies the double-tube circulation reactor proposed by existing patents. At the same time, the single-component catalyst is improved. The process of the reaction system is simple, the equipment investment is small, and the operation is convenient. The binary catalyst system has changed the previous gas, liquid and solid three-phase suspension catalytic system into a gas and liquid homogeneous catalytic system, which improves the activity, prolongs the life of the catalyst, and improves the The operating conditions have solved the problem of clogging, and the operating state has been improved from the previous single-pot single-shift operation to more than hundreds of hours of continuous operation, and the production rate of DMC has been improved, the process has been simplified, and flash evaporation and centrifugal separation have been omitted. Steps such as catalyst single-batch operation recovery have improved economic benefits.

Example 1

Put 10 kg of industrial-grade cuprous chloride and 3 kg of industrial-grade magnesium chloride into a tubular reactor with a total volume of 200 liters, load 80 kg of methanol, start the compressor to press CO gas, start the _O2 compressor to press _O2 Gas, keep the _O2 content at 6%, the total pressure is 2.5MPa, add steam into the casing and heat to 90 °C, the reaction starts, collect the liquid in the gas condenser, and the separated CO+ _O2 mixed gas enters the gas inlet to circulate Use, after half an hour, the system enters a steady state, in the separated liquid mixture, the DMC content is 17.5%, methanol is 79.0%, H ₂ O is 3.5%, and other organic by-products are less than 0.05%. Enter the next section for separation to obtain DMC with a content of 99.5%. After running for 10 hours, the catalyst yield is 0.6gDMC/gCat.h. After running for 100 hours, the catalyst yield is 0.5gDMC/gCat.h. Run 200 After hours, the yield was 0.45 gDMC/gCat.h. Example 2

Put 13kg of industrial grade CuCl and 3kg of KCl into the reactor, start the reaction according to the method described in Example 1, and enter the normal reaction at 130°C, 2.7MPa, CO: O ₂ =93:7, and after 1 hour, The DMC content in the crude product is 15.5%. After running for 10 hours, the catalyst productivity is 0.53gDMC/gCat.h, and after running for 100 hours, the productivity is 0.45gDMC/gCat.h.

Claims (4)

1. processing method by methyl alcohol, oxygen, carbon monoxide liquid-phase carbonylation Synthesis of dimethyl carbonate, its characteristic is to use axial, the single tube reactor of forming by liquid phase section and vapour phase section, its liquid phase section and vapour phase section account for 2/3 and 1/3 of length overall respectively, the caliber of vapour phase section is 1.5～2 times of liquid phase section pipe, liquid phase section caliber 0.1～0.5m, and length is 2～6m, reactor is by corrosion resistant alloy material, or the composite material of corrosion-resistant material lining is formed; And use and help catalytic double-component catalyst system, described double-component catalyst system is by Catalysts Cu Cl and promotor MgCl ₂, CaCl ₂, ZnCl ₂, any composition in the KCl compound, the mole proportioning of CuCl and promotor is 1: 0.5～1: 1.5.

2. method according to claim 1, the process that it is characterized in that the processing method of indication is, reactant methanol, oxygen, carbon monoxide all enter from reactor bottom, reaction product methylcarbonate, water and unstripped gas are discharged from the vapour phase top, after separating, unreacting gas, liquid raw material enter reactor more respectively and react.

3. method according to claim 1 is characterized in that the weight concentration of dual-component catalyst in reaction mass of indication is 2-20%.

4. method according to claim 1 is characterized in that the synthetic reaction condition of indication is: 80～200 ℃ of temperature of reaction, and reaction pressure 1.0～4.0MPa, the concentration of CO is 80～95%, O ₂Concentration be 1～15%.